Energy efficiency improvement was an important phenomenon in the global energy balance over the past 30 years. Without energy efficiency improvements, the OECD nations would have used approximately 49% more energy than was actually consumed as of 1998. This paper first reviews energy intensity trends for the major OECD nations since 1973, considering how much of the overall reduction in E/GDP was due to energy efficiency improvement and how much was due to structural change. The bulk of the paper examines the energy efficiency policies and programs adopted in Japan, United States, and Western Europe, commenting on their effectiveness and efficiency policies and programs adopted in California. This energy savings impacts where possible, The paper also reviews the energy experience shows that well-designed policies call result in substantial energy savings, as demonstrated in the United States where nine specific policies and programs reduced primary energy use in 2002 by approximately 11%. Substantial energy savings also occurred in Japan, some European Countries, and ill the electricity sector ill California. (c) 2005 Elsevier Ltd. All rights reserved.